/Engine/Source/Runtime/HeadMountedDisplay/Public/IHeadMountedDisplayVulkanExtensions.h
If true and VK_PRESENT_MODE_MAILBOX_KHR is not available, VK_PRESENT_MODE_IMMEDIATE_KHR will be preferred over VK_PRESENT_MODE_FIFO_KHR when creating the swap chain for the spectator window.
virtual bool ShouldDisableVulkanVSync() const